Polyadenylation of mRNA as a novel regulatory mechanism of gene expression in temporal lobe epilepsy

Abstract

Temporal lobe epilepsy is the most common and refractory form of epilepsy in adults. Gene expression within affected structures such as the hippocampus displays extensive dysregulation and is implicated as a central pathomechanism. Post-transcriptional mechanisms are increasingly recognized as determinants of the gene expression landscape, but key mechanisms remain unexplored. Here we show, for first time, that cytoplasmic mRNA polyadenylation, one of the post-transcriptional mechanisms regulating gene expression, undergoes widespread reorganization in temporal lobe epilepsy. In the hippocampus of mice subjected to status epilepticus and epilepsy, we report >25% of the transcriptome displays changes in their poly(A) tail length, with deadenylation disproportionately affecting genes previously associated with epilepsy. Suggesting cytoplasmic polyadenylation element binding proteins (CPEBs) being one of the main contributors to mRNA polyadenylation changes, transcripts targeted by CPEBs were particularly enriched among the gene pool undergoing poly(A) tail alterations during epilepsy. Transcripts bound by CPEB4 were over-represented among transcripts with poly(A) tail alterations and epilepsy-related genes and CPEB4 expression was found to be increased in mouse models of seizures and resected hippocampi from patients with drug-refractory temporal lobe epilepsy. Finally, supporting an adaptive function for CPEB4, deletion of Cpeb4 exacerbated seizure severity and neurodegeneration during status epilepticus and the development of epilepsy in mice. Together, these findings reveal an additional layer of gene expression regulation during epilepsy and point to novel targets for seizure control and disease-modification in epilepsy.

CPEB alteration and aberrant transcriptome-polyadenylation lead to a treatable SLC19A3 deficiency in Huntington’s disease

“…Altered CPEBs and subsequent alteration in transcriptome polyadenylation have been associated to the aetiology of various diseases such as cancer (12,13), chronic liver disease (14), epilepsy (15) or autism (8), thus leading to the identification of new possible therapeutic targets among CPEB-dependent dysregulated genes. However, a potential role of CPEBs in neurodegenerative disorders has not been fully explored.…”

High concordance between hippocampal transcriptome of the mouse intra‐amygdala kainic acid model and human temporal lobe epilepsy

“…48 Although our IPA analysis has focused primarily on transcription factors, other mechanisms may also impact on mRNA levels, such as microRNAs or mRNA polyadenylation among many others. 31,32,49 Possible limitations of our study include that gene expression has only been analyzed shortly post-SE and once epilepsy was already established, omitting the seizure-free latent period. The latent period in the IAKA mouse model is, however, almost absent, 17 and the process of epileptogenesis is ongoing beyond the occurrence of the first epileptic seizure.…”

“…p53 has previously been linked to seizure generation and cell death in the IAKA model 48 . Although our IPA analysis has focused primarily on transcription factors, other mechanisms may also impact on mRNA levels, such as microRNAs or mRNA polyadenylation among many others 31,32,49 …”

“…Eight micrograms of cDNA from each sample was fragmented and labeled with GeneChip Mapping 250K Nsp assay kit (Affymetrix, 900753). Hybridization was performed for 16 hours at 45°C 31,32 . Washing and staining steps were performed in the GeneAtlas Fluidics Station (Affymetrix, 00‐0079), following the specific script for Mouse MG‐430 PM Arrays.…”

“…Hybridization was performed for 16 hours at 45°C. 31,32 Washing and staining steps were performed in the GeneAtlas Fluidics Station (Affymetrix, 00-0079), following the specific script for Mouse MG-430 PM Arrays. Arrays were scanned with GeneAtlas Scanner, and CEL files were done using GeneAtlas software (Affymetrix).…”